1. Technical Field
The present invention relates to an ion implanting apparatus that is capable of irradiating an ion beam over a semiconductor wafer to implant ion species, and in particular, relates to an ion implanting apparatus that is capable of forming a beam geometry by passing an ion beam through a through hole of a member.
2. Related Art
Currently, an ion implanting apparatus is utilized for implanting ion species into a semiconductor wafer. Such ion implanting apparatus is described as follows in reference to FIG. 10 and FIG. 11. An ion implanting apparatus 100 shown here includes a main part that comprises an ion gun 110, an aperture member 120, a wafer holding unit 130 or the like, which are linearly arranged.
The ion gun 110 produces ion species supplied from an ion source (not shown) to create an ion beam. The aperture member 120 is formed by, for example, machining carbon graphite, and is provided with a slit-shaped through hole 122 formed in a flat member body 121.
The wafer holding unit 130 includes a rotation stage 131 and a slide mechanism (not shown), and the rotation stage 131 holds a plurality of silicon wafers 140 that are to be processed. The rotation stage 131 revolves a plurality of silicon wafers 140 that are held thereon, and the slide mechanism reciprocates the rotation stage 131 along a vertical direction.
In the ion implanting apparatus 100 having the above-described configuration, an ion beam emitted by the ion gun 110 passes through the through hole 122 of the aperture member 120, so that a beam is shaped to have the corresponding geometry.
A plurality of silicon wafers 140 that are revolved and vertically reciprocated by the wafer holding unit 130 are consecutively exposed over the ion beam having such beam geometry, so that the ion species is equivalently injected over the entire surfaces of a plurality of silicon wafers 140.
The aperture member 120 as described above may alternatively be referred to as, for example, a resolving aperture, a beam aperture, a slit member or the like, and, regardless of the name of the member, the member is composed of a flat member provided with a slit-shaped through hole 122 formed therein, as shown in FIG. 11.
Currently, various proposals for ion implanting apparatuses as described above are made (see, for example, Japanese Patent Laid-Open No. H10-25,178 (1998), Japanese Patent Laid-Open No. H11-149,898 (1999) and Japanese Patent Laid-Open No. H11-283,552 (1999)).
Further, an ion implanting apparatus is also proposed which is configured such that at least a surface of various members located in paths for an ion beam is formed of high purity silicon (not shown). In this ion implanting apparatus, even if particles of contaminants are generated from the members in the paths for the ion beam, the particle is necessarily composed of high purity silicon, and, therefore, a contamination of a silicon wafer can be prevented.
In addition to above, it is disclosed in the related art documents that the above-described high purity silicon may be composed of amorphous silicon deposited on the member surface by a chemical vapor deposition (CVD) process, amorphous silicon deposited by a sputter process, a silicon grown by an epitaxy process or the like (see, for example, Japanese Patent Laid-Open No. H03-269,940 (1991).
Since a gas of ion species is constantly generated in a periphery of an ion beam in the ion implanting apparatus 100 as described above, the ion species is deposited to form a thin film on an inner surface of the through hole 122 of the aperture member 120, as shown in FIG. 12, during the long term operation.
Then, the thin film deposited on the inner surface of the through hole 122 of the aperture member 120 may be peeled off by exposing thereof with the ion beam, and may be eventually scattered to a silicon wafer 140 as a contaminant, as shown in FIG. 13.
In this case, the above-described contaminant may adhere onto a surface of the silicon wafer 140, or may generate damage in the surface of the silicon wafer 140 by a collision of the contaminant, eventually necessitating the disposal of the silicon wafer 140.
For example, a high-current ion implanting apparatus (not shown) or the like utilizes a batch system that retains a large number (e.g., 13 pieces) of silicon wafers 140 therein, and therefore, once a failure is generated as described above, a large number of silicon wafers 140 should be disposed at the same time.
In addition to above, while contaminants generated from the member are composed of silicon in the case of employing the ion implanting apparatus described in the aforementioned Japanese Patent Laid-Open No. H03-269,940, when the contaminants collide with a surface of a silicon wafer, damages may be generated therein. Even if no damage is generated, the presence of contaminants of silicon adhered onto the surface of the silicon wafer may cause a failure in the later semiconductor process.